Document how cache scoping works with tags

[dabrahams]

The documentation says that caches are scoped to branches. Suppose I am building from a tag? The tag might be at the tip of one or more branches, or it might not be at the tip of any branch. How does it decide which caches are in scope? This information should be in the documentation. See also #1178, #79, #1175

Thanks!

[tothambrus11]

I think https://docs.github.com/en/actions/reference/dependency-caching-reference#restrictions-for-accessing-a-cache may answer your question.

[dabrahams]

It doesn't answer whether any branch caches are available to a tag test.

[antonoff]

https://github.com/actions/cache/issues/1342

[antonoff]

[antonoff]

smartcars.json